Position information of individual nodes is useful in implementing functions such as routing and querying in ad-hoc networks. Deriving position information by using the capability of the nodes to measure time of arrival (TOA), time difference of arrival (TDOA), angle of arrival (AOA) and signal strength have been used to localize nodes relative to a frame of reference. The nodes in an ad-hoc network can have multiple capabilities and exploiting one or more of the capabilities can improve the quality of positioning. In this paper, we show how AOA capability of the nodes can be used to derive position information. We propose a method for all nodes to determine their orientation and position in an ad-hoc network where only a fraction of the nodes have positioning capabilities, under the assumption that each node has the AOA capability.

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Ad hoc positioning system (APS) using AOA

The Global Positioning System (GPS) is a satellite-based navigation and time transfer system developed by the U.S. Department of Defense. It serves marine, airborne, and terrestrial users, both military and civilian. Specifically, GPS includes the Standard Positioning Service (SPS) which provides civilian users with 100 meter accuracy, and it serves military users with the Precise Positioning Service (PPS) which provides 20-m accuracy. Both of these services are available worldwide with no requirement for a local reference station. In contrast, differential operation of GPS provides 2- to 10-m accuracy to users within 1000 km of a fixed GPS reference receiver. Finally, carrier phase comparisons can be used to provide centimeter accuracy to users within 10 km and potentially within 100 km of a reference receiver. This advanced tutorial will describe the GPS signals, the various measurements made by the GPS receivers, and estimate the achievable accuracies. It will not dwell on those aspects of GPS which are well known to those skilled in the radio communications art, such as spread-spectrum or code division multiple access. Rather, it will focus on topics which are more unique to radio navigation or GPS. These include code-carrier divergence, codeless tracking, carrier aiding, and narrow correlator spacing.

Global Positioning System: Signals, Measurements, and Performance

We present a new approach to remote sensing of water vapor based on the global positioning system (GPS). Geodesists and geophysicists have devised methods for estimating the extent to which signals propagating from GPS satellites to ground-based GPS receivers are delayed by atmospheric water vapor. This delay is parameterized in terms of a time-varying zenith wet delay (ZWD) which is retrieved by stochastic filtering of the GPS data. Given surface temperature and pressure readings at the GPS receiver, the retrieved ZWD can be transformed with very little additional uncertainty into an estimate of the integrated water vapor (IWV) overlying that receiver. Networks of continuously operating GPS receivers are being constructed by geodesists, geophysicists, government and military agencies, and others in order to implement a wide range of positioning capabilities. These emerging GPS networks offer the possibility of observing the horizontal distribution of IWV or, equivalently, precipitable water with unprecedented coverage and a temporal resolution of the order of 10 min. These measurements could be utilized in operational weather forecasting and in fundamental research into atmospheric storm systems, the hydrologic cycle, atmospheric chemistry, and global climate change. Specially designed, dense GPS networks could be used to sense the vertical distribution of water vapor in their immediate vicinity. Data from ground-based GPS networks could be analyzed in concert with observations of GPS satellite occultations by GPS receivers in low Earth orbit to characterize the atmosphere at planetary scale.

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GPS Meteorology: Remote Sensing of Atmospheric Water Vapor Using the Global Positioning System

Many ad hoc network protocols and applications assume the knowledge of geographic location of nodes. The absolute location of each networked node is an assumed fact by most sensor networks which can then present the sensed information on a geographical map. Finding location without the aid of GPS in each node of an ad hoc network is important in cases where GPS is either not accessible, or not practical to use due to power, form factor or line of sight conditions. Location would also enable routing in sufficiently isotropic large networks, without the use of large routing tables. We are proposing APS - a distributed, hop by hop positioning algorithm, that works as an extension of both distance vector routing and GPS positioning in order to provide approximate location for all nodes in a network where only a limited fraction of nodes have self location capability.

/pdf/ad-hoc-positioning-system-aps-3roowtu3q3.pdf

Ad hoc positioning system (APS)

Many ad hoc network protocols and applications assume the knowledge of geographic location of nodes. The absolute position of each networked node is an assumed fact by most sensor networks which can then present the sensed information on a geographical map. Finding position without the aid of GPS in each node of an ad hoc network is important in cases where GPS is either not accessible, or not practical to use due to power, form factor or line of sight conditions. Position would also enable routing in sufficiently isotropic large networks, without the use of large routing tables. We are proposing APS --- a localized, distributed, hop by hop positioning algorithm, that works as an extension of both distance vector routing and GPS positioning in order to provide approximate position for all nodes in a network where only a limited fraction of nodes have self positioning capability.

/pdf/dv-based-positioning-in-ad-hoc-networks-12d026gqcv.pdf

DV Based Positioning in Ad Hoc Networks

Apparatus to determine the position of a user terminal, the apparatus having corresponding methods and computer-readable media, comprises a receiver to receive, at the user terminal, a wireless orthogonal frequency-division multiplexing (OFDM) signal comprising a scattered pilot signal; and a processor to determine a pseudo-range based on the scattered pilot signal; wherein a position of the user terminal is determined based on the pseudo-range and a location of a transmitter of the OFDM signal.

Position location using digital video broadcast television signals

A method and computer program product for determining the position of a user terminal includes receiving at the user terminal a plurality of digital television (DTV) broadcast signals from a plurality of DTV transmitters, wherein each of the DTV signals is a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting-Terrestrial (DVB-T) signal; determining a pseudo-range between the user terminal and each DTV transmitter based on the DTV broadcast signals based on a known component in the DTV signals; and determining a position of the user terminal based on the pseudo-ranges and a location of each of the DTV transmitters.

Position location using terrestrial digital video broadcast television signals

Future generations of GPS space vehicles (SVs) will have three civil signals instead of the present single civil signal at the L1 frequency of 1575.42 MHz. These future-generation GPS SVs will have a second civil signal centered at the L2 frequency of 1227.6 MHz. The largest improvement in civil user performance, however, will be obtained via the third civil signal at the L5 frequency of 1176.45 MHz. This L5 signal is a new higher-performance civil signal having both a data-free component and a quadrature data modulated component. Both components are modulated with separate pseudorandom noise (PN) codes having a PN-chip clock rate of 10.23 Mcps and a period of 10230 chips or 1 ms. This paper describes the proposed new civil codes for the data-free and data channels and their multiple access properties, and presents block diagrams of possible SV modulators and user receivers.

Proposed new l5 civil gps codes

Proposed New Civil GPS Signal at 1176.45 MHz

A paging/messaging system using the L3 transmission channel of a constellation of GPS satellites orbiting the earth, is comprised of an earth-based injection terminal having a source of paging/messaging signals and a radio transmitter for broadcasting paging/messaging on the L3 transmission channel to in-view ones of the constellation of GPS satellites. A plurality of earth-based mobile receiving stations, each mobile receiving station having an omnidirectional receiving antenna and an L3 transmission channel receiver for receiving the L3 transmission channel broadcasts from the in-view ones of the constellation of GPS satellites and demodulating and decoding to recover the paging/messaging signals, a display as used to present the paging/messaging signals to a designated user the recovered paging/messaging signals. At least one of said earth-based mobile receiving stations includes GPS position receiver for receiving GPS signals from the in-view satellites and determining the position of the mobile receiving station, and presenting the position information to the user on the display.

James J. Spilker

Papers

Position location using digital video broadcast television signals

Position location using terrestrial digital video broadcast television signals

Proposed new l5 civil gps codes

Proposed New Civil GPS Signal at 1176.45 MHz

Paging/messaging system using GPS satellites